Packaging is considered by many in the industry to be the pacing technology for integrated circuit development. As integrated circuit board density continues to increase, integrated circuit package dimensions and tolerances become more critical.
Integrated circuit packages are usually sealed from the environment by joining and aligning a package base or chip carrier to a package lid via a sealing material and a sealing fixture. During this critical joining and alignment operation between the chip carrier and package lid, the final package dimensions are determined.
The sealing process is accomplished by placing the chip carrier and package lid into the sealing fixture and then usually placing the combination into an oven to cure the sealing material. The most common sealing materials used include glasses, solders and epoxy. The sealing fixture's primary function is to align all package components to within the required specifications.
Prior art designs of sealing fixtures include fixtures having openings or windows into which the chip carriers and lids are placed. The fixtures are then horizontally placed into an oven and rely on gravity to provide intimate contact between the chip carrier, sealing material and lid. Alignment accuracy in such processes is dependent upon the worst case tolerances of the IC package as well as those of the fixture.
Other prior art designs include sealing fixtures which are made up of two or more parts. The first part, often called a process boat, is used in packaging assembly steps prior to sealing, i.e. wire bond and die attach. The second part often called an alignment cover is fitted onto the process boat just before sealing and aligns the lid to the chip carrier. In this design, alignment accuracy is also dependant on the worst case tolerances of the alignment cover.
Another common sealing fixture is a simple clip or an arrangement of clips which holds the IC package components together under slight pressure during the sealing process.
As the demands for integrated circuit package dimensions and tolerances continue to increase with increasing circuit board densities, many prior art sealing fixtures can no longer produce sealed IC packages which meet those demands. This results in the need for a sealing fixture capable of producing finished sealed packages with greater alignment accuracy. In addition, such a fixture should lend itself to automated high volume production.